The dihydric phenols have achieved significant success in their commercial applications. The dihydric phenols are used in the commercial manufacture of various polymers including the polyarylates, polyamides, epoxies, polyetherimides, polysulfones and the polycarbonates. Significant attention has been directed to the commercial preparation of the dihydric phenols. For many years it was well known that the acid catalyzed reaction of phenol with a specific aldehyde or ketone would prepare the 4,4'-dihydric phenol with specific groups derived from the aldehyde or the ketone connecting the two phenolic rings. In order to make certain polymers, in particular the polycarbonates, the dihydric phenol must be particularly pure as well as the process particularly efficient since the dihydric phenol cost contributes substantially to the cost of the final polymer. A significant amount of by-product water is formed in many, if not all, of these processes. In order to recycle the water or discharge to a waste treatment facility, it should be as clean as possible of various contaminants which are also prepared in the process. One of the usual contaminants of the by-product water in the dihydric phenol processes is the starting phenol.
It has now been found that phenol can be effectively removed from the aqueous by-product stream accompanying the process. This removal is accomplished by using specific reagents already present in most, if not all, of the dihydric phenol commercial processes.